1. Field of the Invention
The invention relates to an infection shield and a calibration or reference device for calibrating a measuring instrument or serving as a reference target. The invention also relates to methods of taking a reading or measurement of a patient or an object using the calibration or reference device.
2. Background of the Related Art
There are a variety of measuring instruments that utilize light to detect physical characteristics or conditions of a material. Some instruments are used by medical personnel to diagnose a condition of a patient.
In the case of medical instruments, the instrument will emit light at one or more wavelengths, and the emitted light is directed toward a target tissue on a patient. Reflected or scattered light that returns from the target tissue, or possibly fluorescent light generated by the target tissue in response to the emitted light, is then collected by the medical instrument and analyzed to determine characteristics of the target tissue, or a condition of the patient.
An example of such a medical instrument is shown in FIG. 1. The instrument 100 includes a trigger 102 for activating the device. When activated, the device emits light at one or more wavelengths from a nose portion 104. Light that is reflected or scattered from the patient is then collected by the nose portion 104 and analyzed to determine a condition of the patient.
Instruments like the one shown in FIG. 1 may require periodic calibration to maintain their accuracy. Over time, the amplitude and/or wavelength of light output by the light source within the instrument can vary due to environmental conditions, or simple aging of the light emitting elements. In addition, a detector of the instrument can have differing sensitivities depending upon environmental conditions or the age of the detector. For instance, a change in temperature of only a few degrees can significantly affect the sensitivity of a light detector.
For the above reasons, it is common to calibrate a medical instrument prior to taking a reading on a patient. Typically, the instrument is aimed at a calibration target having known optical properties. Light is then scattered or reflected by the calibration target and received back in the instrument. Because the calibration target has known optical properties, the instrument is able to perform a calibration operation to ensure that the instrument continues to deliver accurate results.
Also, some measuring instruments use a reference target as part of a measurement process. In such a device, the instrument is aimed at a reference target having known optical properties. Light from the instrument is scattered or reflected from the reference target, and a reading is taken. The results of the measurement operation conducted on the reference target can then be used as a standard or reference against which patient measurements are judged. For instance, the result of a patient reading could be derived by determining a difference or ratio between a patient reading and a reading of the reference target. Because the optical properties of the reference target are known, variations in light output or detector sensitivity can be accounted for by use of the reference target.
When such an instrument is used with human or animal patients, steps must be taken to ensure that use of the instrument does not contaminate or infect a patient. When the instrument is successively used to examine two different patients, steps must be taken to ensure that there is no cross contamination between the patients.